It is often said of international agreements that the devil is in the detail. If a Middle East peace conference is held later this year it will be the other way round: the devil will be in the principle. The three most intractable of these principles are the borders of Israel, the status of Jerusalem and fate of more than 5 million Palestinian refugees. On each a gulf of understanding opens up so wide as to destroy any attempt to enlist the support of even those Arab states that have made bilateral peace deals with Israel, such as Jordan and Egypt, let alone seek the help of Saudi Arabia or Syria, which have yet to do so. And yet on each a pragmatic solution is within reach.

Yesterday it emerged that Syria is likely to reject the US invitation to attend the conference. Saudi Arabia may also bow out or limit the status of its representation. One can understand why. Riyadh is being asked to reverse its policies on Israel, without knowing what it will receive in return for the legitimacy it gives by participating in the process. Israel says that the conference will set a horizon for a future Palestinian state, which would then be followed by hard negotiations on concrete issues. Tony Blair, in his new role as envoy to the Middle East Quartet, talked in a similar vein on Sunday of establishing the "contours" of a Palestinian state.

What if the conference takes place, but hard negotiations fail to materialise? What if all that emerges is a series of vaguely worded statements, giving the appearance of change without enabling it to happen? If the leaders of Arab states have difficulty understanding what they would get from this conference, what chance would they have of selling the deal to the wider Arab world? The risk of attempting an impressionist painting is that you end up with a canvas full of blurs. There are concrete measures that can be taken which fall short of addressing the core issues but which would still have a tangible effect. Israel could freeze all settlements, which have doubled between the Oslo accords and the second intifada.

As things stand, short-term tactical considerations stand in the way of the strategic goal. Israel has defined its strategic interest as isolating Hamas in Gaza and supporting Mahmoud Abbas in the West Bank. But even that is being undermined by the virtual lockdown that Israel's army imposes on Palestinians moving round the West Bank. As a prime ministerial contender, Ehud Barak's interest lies in lifting the checkpoints. As the serving defence minister, he would be the first to blamed if a suicide bomber got through. The alternative is to build peace from the bottom up with a series of achievable but significant measures.